2. Form under the surface of the earth,
cooling very slowly to form large batholith
Exposed after millions of years of erosion
Rock has low porosity and permeability but water easily pass
through joints
Joints are cracks formed during cooling and shrinking of the magma
Cracks are further enlarged by pressure release
Three main minerals:
Quartz
Feldspar
Mica
3.
4. Freeze thaw action occurring in joints of highland areas
Feldspars in granite are easily weathered by hydrolysis
Quartz is tough mineral which will not be weathered
and will be left behind
The minerals are made of different colours,
– they are susceptible to insolation weathering and
resulted in granular disintegration.
5. Theories of Tor formation:
1. Initial formation of vertical joints in the granite
2. Removal of overlying rock (2-3m thick) and creation
of horizontal joints
3. Sub-surface chemical weathering widening the joints
( Hydrolysis resulting in kaolinisation)
4. Deep weathering of granite
5. Frost shattering and exposure of granite by
solifluction in periglacial times
6.
7.
8.
9.
10.
11.
12.
13. Taught to have been formed by weathering deep
underground before granite became expose on the
surface
1. Despite being very strong, granite is very vulnerable
to chemical weathering, Feldspar readily reacts with
acidic water to form kaolin and this hydrolysis process
weaken the granite causing it to crumble apart
2. Granite is heavily jointed and the density of
jointing is believed to have been a critical factor
14.
15. Formed from the remain of organic matter, usually
seashells and plants
Formed under the sea, over 200 millions ago
Limestone rock has no pore spaces because the rock is
so old.
Layers of limestone become very compressed and
cemented under the weight of overlying sediments
Very strong and resistant to erosion
Able to form steep slopes without collapsing
16. Has large numbers of joints and bedding planes
These lines of weaknesses allow water to pass
through the rock to produce Karst scenery
Composed mainly of mineral calcium carbonate
which is insoluble
The main processes, which affect it are carbonation
and solution
17. 1. Surface features caused by solution:
Limestone pavement
- large area of bare exposed rock
- When overlying rock was eroded, the pressure release
on limestone below caused it to crack even more.
- Characterise by large gaps between the rock called
grikes.
- The remaining blocks are called clints .
21. 2. Drainage Features:
Swallow holes and sink holes are where river flow down
into the rock.
Sink holes are relatively small while
Swallow holes are larger
Both have been formed by constant chemical attack of
water on joints or by the collapse of a cavern below
22.
23.
24.
25.
26. 3. Surface features resulting from underground drainage
Poljes - in the tropics, the landscape may be composed
of either cone shaped hills and polygonal
depressions
E.g. ‘cockpit country’ (Jamaica)
Tall isolated towers rising from wide plains - (Guilin, China)
Dry valleys – a river valley without a river.
a common feature on chalk and limestone
27.
28.
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30.
31.
32.
33.
34. 4. Underground features and underground depositional features
Cavern - underground caves that have been hallowed
out by the action of underground streams and
by carbonation and solution.
Three distinctive features:
Stalactites – hang from the roof of the cavern, and basically lime deposits
Stalagmites – grow from the floor and also lime deposits
Pillars – where stalactites and stalagmites have joined
